Supercapacitor Performance Of Metal Oxide/Graphene And Ni-MOF

With the development of energy,supercapacitors are gradually becoming one of the energy storage devices with high application prospects in the future due to the properties of both chemical batteries and traditional capacitors.The performance of supercapacitors mainly depend on electrode materials,which have been one of the research hotspots these years.Transition metal oxides have the advantages of high theoretical specific capacity,abundant resources,and less damage to the environment;whereas graphene materials show high mechanical stability and high electrical conductivity.As metal oxide/graphene materials may possess both advantages mentioned above,the main research contents and results of this work are as following:Firstly,Fe₂O₃/reduced graphene oxide aerogel?Fe₂O₃/rGOA?are prepared by a simple hydrothermal process.Its morphology and microstructure are characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?and transmission electron microscopy?TEM?.Electrochemical properties are investigated using cyclic voltammetry and galvanostatic charge/discharge.It is found that the particles of Fe₂O₃ have the size distribution in the range of 30 to 50 nm and its average size is hardly affected by the amount of Fe₂O₃ loaded into rGOA.An interconnected 3D network structure is formed by the self-assembly of graphene oxide sheets decorated with Fe₂O₃ nanoparticles.The as-prepared Fe₂O₃/rGOA composites show good cyclic performance and coulomb efficiency with specific capacitance as 627 and 522 F/g at 1 and 20 A/g within the operated voltage window?-1.1 to 0.3 V?.Secondly,the composites of NiCo₂O₄/reduced graphene oxide nanosheets?NiCo₂O₄/rGO?are prepared via a facile hydrothermal route followed by calcination.Electrochemical properties are investigated using cyclic voltammetry and galvanostatic charge/discharge.It is found that the composite materials show a sea urchin-like structure.In comparison with pure NiCo₂O₄,the specific capacity and rate performance of the as-made NiCo₂O₄/rGO composites have been significantly improved.This is mainly attributed to the composite structure with high porosity formed during the fabrication process of the NiCo₂O₄/rGO nanocomposites.The NiCo₂O₄/rGO shows good cyclic performance and coulomb efficiency with a specific capacitance over 650 F/g at a current density of 0.5 to 3.0 A/g within the window?0 to 0.5 V?.The materials can be considered as a promising electrode material for surpercapactiors.Finally,Ni-based metal organic frameworks?Ni-MOFs?and its derivatives are also prepared by the hydrothermal method.The electrochemical properties of the materials are extensively studied.A specific capacitance of 866 F/g is obtained at a current density of 0.5A/g for Ni-MOFs.Furthermore,the Ni-MOF derived nickel sulfides show excellent capacitance performance and coulomb efficiency with specific capacitance as 1574 and 696 F/g at 1 and 10A/g.